JP2006210119A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of enhancing extraction efficiency of light emitted from an EL element and entered in a transparent substrate. <P>SOLUTION: A lighting system 10 is provided with a transparent substrate 11 and a plurality of organic EL elements 12. In the transparent substrate 11, a plurality of light entering parts 14 are formed on the face opposite to the light emitting face 13, and the organic EL element 12 is provided so that its light emitting sides face each other for every and each light entering part 14. The light entering part 14 is each formed in a truncated cone shape so that its diameter shrinks as it approaches toward the organic EL element 12 side, and the inclination angle θ of the slope 15 of the light entering part 14 is 55-80 degrees. In addition, the ratio of the area S1 of the light emitting face 12a of the organic EL element 12 to the area S2 of the end face 14b opposite to the end face 14a on the organic EL element 12 side of the light entering part 14, S1/S2, is not more than 0.49. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device, and more specifically, a transparent substrate in which a plurality of light incident portions are formed on a surface opposite to an emission surface, and an electrometer provided so that the light emission sides face each other. The present invention relates to a light emitting device including a luminescence element.

  2. Description of the Related Art Conventionally, there has been proposed a lighting device including an electroluminescence element (hereinafter, the electroluminescence element may be referred to as an EL element) on a transparent substrate as a backlight of a liquid crystal display device. The light emitted from the EL element is emitted in all directions. Accordingly, in an illuminating device in which an EL element is formed on a transparent substrate, the angle of light incident on the transparent substrate from the EL element varies, and a part of the light incident on the transparent substrate is an emission surface of the transparent substrate. And cannot be emitted from the transparent substrate. That is, there is a problem that the light extraction efficiency from the transparent substrate of the light incident on the transparent substrate from the EL element is low.

  As a technique for solving this problem, an EL element in which a microlens array element is provided on the exit surface of a transparent substrate has been proposed (see Patent Document 1). As shown in FIG. 7, the EL element 50 includes a transparent substrate 51, a transparent electrode 52 formed on the lower surface of the transparent substrate 51, an EL light emitting layer 53 formed on the lower surface of the transparent electrode 52, and an EL light emitting layer. The rear surface electrode 54 is formed on the lower surface of 53, and the minute lens array element 55 is provided on the emission surface of the transparent substrate 51. The micro lens array element 55 is composed of a large number of conical or quadrangular pyramidal lens elements 55a formed adjacent to each other.

  Further, as shown in FIG. 8 (a), on a substrate (base body) 61 formed of a light transmissive material, a contour defining body 63 separated by a groove 62 and formed in a quadrangular pyramid shape is provided. An illuminating device 60 having a light emitting means 64 on a contour defining body 63 has been proposed (see Patent Document 2). Each contour defining body 63 may be configured such that light from the light emitting means 64 irradiated on the inside thereof is totally reflected on the slope (side surface) 65 within the contour defining body 63, or as the light emitting means 64. It describes that an EL element may be used.

In addition, an organic EL panel for a display device that can improve the light utilization efficiency and obtain a bright image has been proposed (see Patent Document 3). As shown in FIG. 8B, in the organic EL panel 70, the organic EL elements 72 to be pixels are formed in a matrix on the first transparent substrate 71, and the organic EL elements 72 are formed on the organic light emitting film. In this structure, two transparent substrates 73 are arranged and these are fixed by an adhesive layer 74. On the surface of the second transparent substrate 73 facing the first transparent substrate 71, a V-groove 75 is formed in a lattice shape except for the pixel portion, and a reflective film 76 is formed on the inclined surface 75a of the V-groove 75. Yes. Light traveling sideways in the second transparent substrate 73 is reflected by the reflective film 76 and emitted from the surface of the second transparent substrate 73.
JP 2003-59641 A Special table 2002-510805 gazette JP 2003-282255 A

  In the configuration of Patent Document 1 in which the microlens array element 55 is arranged on the exit surface of the substrate, only light with a specific incident angle is emitted from the transparent substrate 51 in the front direction (upward in FIG. 7), and other than the specific incident angle. The light repeats total reflection on the emission surface and reflection on the back electrode 54 (metal electrode), and emits in the front direction when a specific incident angle is reached. Therefore, since the light extraction efficiency depends on the reflectance of the back electrode 54, the light extraction efficiency is low with a metal electrode having a reflectance other than 100%.

  Further, in the case of the configuration of Patent Document 2 or Patent Document 3, the light that travels laterally through the substrate out of the light incident on the transparent substrate from the EL element is reflected so as to be emitted from the exit surface of the substrate on the slope. Therefore, the light extraction efficiency is not significantly affected by the reflectance of the metal electrode. However, in the configuration of Patent Document 3, since the light is reflected by the reflective film 76 provided on the slope, the reflectance of the reflective film 76 affects the light extraction efficiency. As described in Patent Document 2, if the configuration is such that light is totally reflected on the slope, the reflectance is improved as compared with the configuration in which a reflective film is provided. However, even if light is emitted from the emission surface of the substrate, it does not contribute to improvement of the luminance in the front direction unless the emission angle is large and it faces the front of the emission surface.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to increase the light extraction efficiency and the luminance in the front direction of the light emitted from the EL element and incident on the transparent substrate, as compared with the conventional apparatus. An object of the present invention is to provide a light-emitting device that can be used.

  In order to achieve the above object, according to the first aspect of the present invention, a transparent substrate having a plurality of light incident portions formed on a surface opposite to the light exit surface is opposed to the light output side for each light incident portion. A light emitting device provided with an EL element. Each of the light incident portions has a truncated cone shape or an elliptic frustum shape with a ratio of a major axis to a minor axis of 2 or less, and is formed so as to be reduced in diameter toward the EL element side. The inclination angle of the inclined surface of the incident portion is 55 to 80 degrees. Further, a ratio S1 / S2 between the area S1 of the light emitting surface of the EL element and the area S2 of the end surface on the opposite side of the EL element side of the light incident portion is 0.5 or less. Here, “conical or elliptical truncated cone shape” is not limited to a truncated cone or elliptical truncated cone, and the intersection line between the plane including the central axis of the truncated cone or elliptical truncated cone and the inclined surface is a curve. Including. Further, “the inclination angle of the inclined surface is 55 to 80 degrees” means that when the intersecting line is a straight line, the angle formed by the intersecting line and a straight line extending in a direction parallel to the end surface of the light incident portion on the electroluminescence element side is 55. Means ~ 80 degrees. When the intersecting line is a curve, a straight line connecting the EL element side end of the curve and a position of 40% from the EL element side end in the thickness direction of the light incident part, or the position of 40% The angle formed by at least one of the straight lines connecting the 80% position from the EL element side end portion and the straight line extending in a direction parallel to the end face of the light incident portion on the electroluminescence element side is 55 to 80 degrees. It means that there is.

  In this invention, the light extraction efficiency of the light emitted from the EL element and incident on the transparent substrate is improved as compared with the conventional device in which the shape of the light incident portion is a quadrangular pyramid shape, and the light extraction efficiency and the front direction are improved. The brightness can be further increased.

  The invention according to claim 2 is the total area of the area S2 of the end face opposite to the end face on the electroluminescence element side of each light incident portion with respect to the area of the exit face of the transparent substrate in the invention according to claim 1. Is 52% or more. According to the present invention, each light incident portion is formed of a quadrangular pyramid, and luminance equal to or higher than the luminance in the front direction when the sides of the EL element side end faces of adjacent quadrangular pyramids are in contact with each other can be obtained. .

  According to a third aspect of the present invention, there is provided a transparent substrate having a plurality of light incident portions formed on a surface opposite to the emission surface, and an EL element provided so that the light emission sides face each other. It is the light-emitting device provided with. The light incident portions are each in the shape of a truncated pyramid (N is a natural number of 6 or more), and are formed so that the area of the end face on the EL element side is smaller than the area of the end face on the opposite side, The inclination angle of the inclined surface of the light incident part is 55 to 80 degrees. Further, a ratio S1 / S2 between the area S1 of the light emitting surface of the EL element and the area S2 of the end surface on the opposite side of the EL element side of the light incident portion is 0.5 or less. Here, the “N-pyramidal frustum shape” is not limited to the N-pyramidal frustum, but also includes those in which the intersection line between the plane including the central axis of the N-pyramidal frustum and the inclined surface is a curve. Further, “the inclination angle of the inclined surface is 55 to 80 degrees” means that when the intersecting line is a straight line, the angle formed by the intersecting line and a straight line extending in a direction parallel to the end surface of the light incident portion on the electroluminescence element side is 55. Means ~ 80 degrees. When the intersecting line is a curve, a straight line connecting the EL element side end of the curve and a position of 40% from the EL element side end in the thickness direction of the light incident part, or the position of 40% The angle formed by at least one of the straight lines connecting the 80% position from the EL element side end portion and the straight line extending in a direction parallel to the end face of the light incident portion on the electroluminescence element side is 55 to 80 degrees. It means that there is. Also in this invention, compared with the case where the shape of the light incident part is a quadrangular pyramid, the extraction efficiency of the light emitted from the EL element and incident on the transparent substrate is improved, and the light extraction efficiency and the front direction are improved. The brightness can be increased as compared with the conventional apparatus.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein an area S1 of the light emitting surface of the electroluminescent element and the electroluminescent element side of the light incident portion are arranged. Ratio S1 / S2 with the area S2 of the end surface opposite to the end surface is 0.25 or less. In this invention, compared with the case where the ratio S1 / S2 is larger than 0.25, it is possible to improve the extraction efficiency and the luminance in the front direction of the light emitted from the EL element and incident on the transparent substrate.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the light incident portion is an intersection of a plane including a central axis thereof and a slope of the light incident portion. The line is formed to be a convex curve outward. In the present invention, it is easy to improve the light extraction efficiency as compared with the case where the intersecting line is a straight line or the intersecting line is an inwardly convex curve.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the electroluminescence element is an organic electroluminescence element. In this invention, it can drive with a low voltage compared with the case where the electroluminescent element is formed with the inorganic electroluminescent element.

  According to the present invention, the extraction efficiency of light emitted from the EL element and incident on the transparent substrate and the luminance in the front direction can be increased as compared with the conventional device.

(First embodiment)
Hereinafter, a first embodiment in which the light-emitting device of the present invention is embodied in a lighting device will be described with reference to FIGS. FIG. 1A is a partial schematic diagram of a lighting device, FIG. 1B is a partial enlarged detail view of FIG. 1A, and FIG. 2 is a schematic diagram showing the arrangement of light incident portions. FIG. 3 is a diagram showing the relationship between the relative luminance and the inclination angle of the slope, and FIG. 4 is a graph showing the influence of the reflectance of the slope on the luminance. 1A and 1B schematically show the structures of the lighting device and the organic electroluminescence element (organic EL element), and some dimensions are exaggerated for the convenience of illustration. For the sake of clarity, the ratio of dimensions such as the width, length, and thickness of each portion is different from the actual ratio.

  As shown to Fig.1 (a), the illuminating device 10 is provided with the transparent substrate 11 and the organic EL element 12 as a some EL element. The transparent substrate 11 has a plurality of light incident portions 14 formed on the surface opposite to the exit surface 13, and the organic EL elements 12 are provided so that the light exit sides face each other. In this embodiment, a glass substrate is used as the transparent substrate 11.

  Each light incident portion 14 is formed in a truncated cone shape and has a reduced diameter toward the EL element side. As shown in FIG. 1B, the light incident part 14 has an inclination angle of the slope 15 of θ, an area of the light emitting surface of the organic EL element 12 as S1, and an end face 14a of the light incident part 14 on the organic EL element 12 side. When the area of the opposite end face 14b is S2, the inclination angle θ is 55 to 80 degrees, and the ratio S1 / S2 between the area S1 and the area S2 is 0.5 or less, preferably 0.25 or less. Is formed. The inclination angle θ of the inclined surface 15 is an angle formed by a line extending between the plane including the central axis of the truncated cone and the inclined surface 15 in a direction parallel to the end surface 14a on the organic EL element 12 side of the light incident portion 14. means. The light incident portion 14 preferably has a diameter of 200 μm or less on the end surface 14 b opposite to the end surface 14 a on the organic EL element 12 side.

  Each light incident portion 14 is disposed such that the adjacent light incident portions 14 are in contact with each other at the periphery of the end face 14b. As shown in FIG. 2, in this embodiment, the light incident portions 14 are arranged in a square lattice shape, that is, the lines connecting the centers of the light incident portions 14 are in a square lattice shape.

  The organic EL element 12 is formed by sequentially laminating a first electrode 16, an organic EL layer 17, and a second electrode 18 from the transparent substrate 11 side. In this embodiment, the first electrode 16 constitutes an anode and the second electrode 18 constitutes a cathode. The organic EL element 12 constitutes a so-called bottom emission type organic EL element in which light from the organic EL layer 17 is extracted (emitted) from the transparent substrate 11 side. In this embodiment, the area of the light emitting surface 12a of the organic EL element 12 is formed to have the same area S1 as the area of the end surface 14a on the EL element side of the light incident portion 14.

The first electrode 16 is made of a known transparent conductive material. For example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), SnO ₂ (tin oxide), etc. Can be used.

The organic EL layer 17 is formed using a known organic EL material, and is configured according to the target emission color of the organic EL element 12.
For the second electrode 18, a conventionally known cathode material, a material similar to the first electrode 16, or the like can be used. For example, a metal such as aluminum, gold, silver, copper, or chromium, or an alloy thereof is used. .

  The organic EL element 12 is provided with a protective part (not shown) for protecting the organic EL layer 17 from oxygen and moisture. The protective part may be a known passivation film, a sealing can, or the like. It is comprised by the combination etc.

Next, the operation of the illumination device 10 configured as described above will be described.
The illumination device 10 is used as a backlight of a liquid crystal display device, for example.
When a DC driving voltage is applied between the first electrode 16 and the second electrode 18 of the organic EL element 12, the organic EL layer 17 emits light, and the light is emitted from the first electrode 16 side which is the light emission side of the organic EL element 12. Light is emitted and incident on the light incident portion 14. Since the organic EL element 12 is isotropic, part of the light incident on the light incident portion 14 travels obliquely with respect to the emission surface 13, not in a direction orthogonal to the emission surface 13 of the transparent substrate 11.

  When light in a medium having a refractive index n1 enters an interface with a medium having a refractive index n2 (n2 <n1), all light rays are reflected when the incident angle is larger than a certain angle. This angle is called the critical angle. Therefore, in the light incident on the transparent substrate 11 from the organic EL element 12, light having an incident angle with respect to the emission surface 13 (an angle formed with the perpendicular of the emission surface 13) larger than the critical angle θc is totally reflected by the emission surface 13. The light cannot be emitted from the transparent substrate 11. The relationship of the following formula is established between the critical angle θc and the refractive indexes n1 and n2.

sin θc = n2 / n1 (1)
Therefore, when the transparent substrate 11 is a glass substrate (refractive index is about 1.5), the refractive index of air is about 1.0, so that the critical angle θc = sin ⁻¹ (1 / 1.5) is critical. The angle θc is about 42 degrees. Of the light incident on the transparent substrate 11 from the organic EL element 12, light having an incident angle with respect to the emission surface 13 of 0 to about 42 degrees is emitted from the transparent substrate 11 according to Snell's law. Light having an incident angle greater than 42 degrees is totally reflected at the exit surface 13, so that such light does not exit from the exit surface 13 when the transparent substrate 11 is flat. However, the light from the organic EL element 12 is incident on the transparent substrate 11 from the truncated cone-shaped light incident portion 14. Since the inclination angle θ of the inclined surface 15 is 55 to 80 degrees, the light incident from the organic EL element 12 at an angle that makes the incident angle on the emission surface 13 larger than 42 degrees is shown in FIG. ), The light is incident obliquely on the inclined surface 15, totally reflected by the inclined surface 15, travels to the emission surface 13 of the transparent substrate 11 so that the incident angle is less than 42 degrees, and is emitted from the transparent substrate 11. .

  Even if light is emitted from the emission surface 13 to the outside, if the emission angle (angle formed with the perpendicular of the emission surface 13) is large, the light is not emitted in the front direction of the emission surface 13, and thus contributes to improvement of the luminance in the front direction. do not do. In order for the light reflected from the inclined surface 15 and traveling toward the emitting surface 13 to be emitted from the emitting surface 13 in a direction that effectively contributes to luminance, the inclination angle θ of the inclined surface 15 needs to be in a specific range. Further, not only the inclination angle θ, but also the ratio S1 / S2 between the area S1 of the light emitting surface 12a of the organic EL element 12 and the area S2 of the end surface 14b on the opposite side of the EL element side of the light incident portion 14 is illuminated. It has been found that the brightness of the device 10 is greatly affected. FIG. 3 shows the relationship between the relative luminance and the inclination angle θ when the ratio S1 / S2 is changed. In the present invention, the Monte Carlo method is performed by changing the ratio S1 / S2 between the area S1 of the light emitting surface of the organic EL element 12 and the area S2 of the end face 14b opposite to the end face 14a of the light incident portion 14 on the organic EL element 12 side. The brightness of the light emitted from the emission surface 13 was examined by the used ray tracing simulation. The relative luminance is relative to the luminance of the EL element having a quadrangular pyramid-shaped lens element whose apex angle is 90 degrees in the configuration proposed in Patent Document 1, that is, the configuration having a quadrangular pyramid-shaped lens element on the emission surface 13. The relative luminance was 1 when the luminance was the same as that of the EL element. From FIG. 3, it was confirmed that when the ratio S1 / S2 is 0.49 or less and the inclination angle θ is 55 to 80 degrees, the luminance is higher than that in the configuration of Patent Document 1. Further, when the ratio S1 / S2 is 0.25 or less and the inclination angle θ is 60 to 75 degrees, the luminance is about twice or more compared to the configuration of Patent Document 1, and the ratio S1 / S2 is 0.25. In the following, it is confirmed that if the inclination angle θ is 60 to 70 degrees, the luminance is about 2.3 times or more compared to the configuration of Patent Document 1. Furthermore, when the ratio S1 / S2 is 0.09 and the inclination angle θ is 60 to 70 degrees, it is confirmed that the luminance is about 2.6 times or more that in the case of Patent Document 1.

  The ratio between the luminance when the light incident portion 14 is a truncated cone having a ratio S1 / S2 of 0.09 and the diameter of the end face 14b being 100 μm, and the luminance when the light incident portion 14 is a quadrangular pyramid with the same area ratio. The effect of the inclination angle θ on the above was investigated by performing a ray tracing simulation. The results are shown in Table 1. From Table 1, it is confirmed that when the inclination angle θ is 55 degrees or more, the luminance of the illumination device 10 is higher than that when the light incident portion 14 is a quadrangular pyramid. In addition, when the inclination angle θ is 65 to 80 degrees, it has been confirmed that the luminance is 1.4 times or more than that when the light incident portion 14 is a quadrangular pyramid.

光入射部１４の斜面１５における光の反射を全反射ではなく、斜面１５に反射膜を設けて反射させる構成とした場合の輝度に対する反射率Ｒの影響を、比Ｓ１／Ｓ２が０．２５で、傾斜角度θが６０度のモデルについて光線追跡シミュレーションを行った結果を図４に示す。なお、反射率９５％の反射膜は、例えば、銀の膜で得られ、反射率９０％の反射膜は、例えば、アルミニウムの膜で得られる。図４から、反射率が９０％でも、輝度が全反射（反射率１００％）に比較して８割に低下することが分かった。即ち、光入射部１４に入射された光を斜面１５で反射させる構成を採る場合、反射膜で反射させる構成に比較して全反射で反射させる方が、効果が高く構造も簡単となる。

The ratio S1 / S2 is 0.25 with respect to the influence of the reflectance R on the luminance when the reflection of the light on the inclined surface 15 of the light incident portion 14 is not totally reflected, but a reflection film is provided on the inclined surface 15. FIG. 4 shows the result of ray tracing simulation for a model having an inclination angle θ of 60 degrees. The reflective film having a reflectivity of 95% is obtained by, for example, a silver film, and the reflective film having a reflectivity of 90% is obtained by, for example, an aluminum film. FIG. 4 shows that even when the reflectance is 90%, the luminance is reduced to 80% compared to the total reflection (reflectance 100%). That is, in the case of adopting a configuration in which the light incident on the light incident portion 14 is reflected by the inclined surface 15, it is more effective and simpler to reflect by total reflection than the configuration of reflecting by the reflective film.

  Regarding the influence of changing the ratio of the total area of the area S2 of the end face 14b of each light incident portion 14 to the filling rate of the light incident portion 14, that is, the area of the exit surface 13 of the transparent substrate 11, the ratio S1 / S2 is 0. Table 2 shows the result of ray tracing simulation for a model having a diameter of 0.09 and an end face 14b of 100 μm and an inclination angle θ of 65 degrees. In Table 2, the relative luminance indicates a value when the luminance is 1 when the light incident portions 14 of the truncated cone are arranged in a square lattice shape. When the light incident portion 14 is formed of a quadrangular pyramid and the sides of the end faces of the adjacent quadrangular pyramids on the organic EL element 12 side are in contact with each other, the relative luminance value is 0.65. From Table 2, it can be seen that when the filling rate is approximately 50% (more precisely 52%) or higher, the luminance higher than that obtained when the light incident portions of the square pyramid are arranged in a square lattice shape can be obtained. In other words, when the light incident portion 14 is formed in a truncated cone, the area of the light emitting surface 12a of the organic EL element 12 is approximately ½ and the same luminance can be obtained as compared with the case where the light incident portion 14 is formed in a quadrangular truncated cone.

この実施の形態では以下の効果を有する。

This embodiment has the following effects.

  (1) The illuminating device 10 includes an EL provided with a transparent substrate 11 having a plurality of light incident portions 14 formed on the surface opposite to the emission surface 13 and the light emission sides facing each light incidence portion 14. Device. The light incident portions 14 are each formed in a truncated cone shape and have a diameter reduced toward the EL element side, and the inclination angle θ of the inclined surface 15 of the light incident portion 14 is 55 to 80 degrees. Further, the ratio S1 / S2 between the area S1 of the light emitting surface of the EL element and the area S2 of the end face 14b on the opposite side of the EL element side of the light incident portion 14 is 0.5 or less. With such a configuration, the light extraction efficiency of the light emitted from the EL element and incident into the transparent substrate 11 is improved as compared with the case where the light incident portion 14 has a quadrangular pyramid shape, and the light extraction efficiency is improved. Can be increased as compared with the conventional apparatus.

  (2) The inclination angle θ of the inclined surface 15 of the light incident portion 14 is set to an angle that totally reflects the light incident on the light incident portion 14 from the EL element so as to travel toward the exit surface 13 when incident on the inclined surface 15. Therefore, the luminance of the emission surface 13 is higher than that in the configuration in which the reflective film is provided on the inclined surface 15.

(3) If the ratio S1 / S2 is 0.25 or less, the luminance in the front direction can be increased as compared with the case where the ratio S1 / S2 is greater than 0.25.
(4) If the ratio S1 / S2 is 0.25 or less and the inclination angle θ is 60 to 75 degrees, the luminance is about twice or more compared to the configuration of Patent Document 1, and the ratio S1 / S2 is set to 0. 0.09 and the inclination angle θ of 60 to 70 degrees, the luminance is about 2.5 times or more compared to the configuration of Patent Document 1.

(5) If the inclination angle θ of the inclined surface 15 of the light incident portion 14 is 55 degrees or more, the luminance of the illumination device 10 becomes higher than when the light incident portion 14 is arranged in a square lattice shape with a quadrangular pyramid.
(6) When the filling factor of the light incident part 14 is set to 52% or more, the luminance of the lighting device 10 is higher than that in the case where the light incident part 14 is arranged in a square lattice shape with the quadrangular pyramid.

(7) The EL element is composed of the organic EL element 12. Therefore, it can be driven at a lower voltage than when an inorganic EL element is used.
(Second Embodiment)
Next, a second embodiment will be described. This embodiment is different from the first embodiment in that the light incident portion 14 is formed not on a truncated cone but on an N pyramid (N is a natural number of 6 or more). The same parts as those in the above embodiment are given the same reference numerals, and detailed description thereof is omitted. The light incident portion 14 is formed such that the area of the end surface 14a on the organic EL element 12 side is smaller than the area of the opposite end surface 14b, and the inclination angle of the inclined surface 15 of the light incident portion 14 is 55 to 80 degrees. is there. The ratio S1 / S2 between the area S1 of the light emitting surface 12a of the organic EL element 12 and the area S2 of the end face 14b opposite to the end face 14a on the organic EL element 12 side of the light incident portion 14 is 0.5 or less.

  Regarding the influence of changing the number of angles with the shape of the light incident portion 14 being a truncated pyramid, a regular polygon inscribed in a square having a ratio S1 / S2 of 0.09 and an end face 14b of 100 μm on one side, and an inclination angle θ of 65 degrees Table 3 shows the result of the ray tracing simulation for this model. In Table 3, the relative luminance indicates a value when the luminance is set to 1 when the light incident portions 14 of the truncated pyramid are arranged in a square lattice shape. When the light incident portion 14 is a truncated cone having a ratio S1 / S2 of 0.09 and a diameter of the end face 14b of 100 μm, the relative luminance value is 1.52. From Table 3, it can be seen that the luminance is improved as the number of corners is increased. However, when the number of corners is larger than 6, the increase rate of the luminance is not increased for the increase of the number of corners.

光入射部１４をＮ角錐台（Ｎは６以上の自然数）に形成することにより、四角錐台の場合に比較して輝度が１．２７倍以上となり、円錐台の場合の輝度の１／２以上となる。第１の実施の形態の図３の結果から、傾斜角度θが６５度の場合、光入射部１４が円錐台では、前記比Ｓ１／Ｓ２が０．４９のときの輝度は、比Ｓ１／Ｓ２が０．０９のときの輝度のほぼ半分である。従って、多角錐台の場合でもほぼ同様な割合で比Ｓ１／Ｓ２が０．４９のときの輝度が得られるとすれば、比Ｓ１／Ｓ２が０．４９のときの輝度は特許文献１の構成の場合より高くなると推定される。

By forming the light incident portion 14 on an N-pyramidal frustum (N is a natural number of 6 or more), the luminance is 1.27 times or more as compared with the case of a quadrangular frustum, and ½ of the luminance in the case of a frustum. That's it. From the result of FIG. 3 of the first embodiment, when the tilt angle θ is 65 degrees, the light incident part 14 is a truncated cone, and the luminance when the ratio S1 / S2 is 0.49 is the ratio S1 / S2. Is about half of the luminance when. Therefore, even in the case of a polygonal frustum, if the luminance when the ratio S1 / S2 is 0.49 can be obtained at a substantially similar ratio, the luminance when the ratio S1 / S2 is 0.49 is the configuration of Patent Document 1. Is estimated to be higher than

Therefore, the second embodiment has the following effects in addition to the effects (2), (5), and (7) of the first embodiment.
(8) The light incident portion 14 is an N-pyramidal frustum (N is a natural number of 6 or more) where the area of the end surface 14a on the organic EL element 12 side is smaller than the area of the end surface 14b, and the inclination angle θ of the inclined surface 15 is 55 to 80 degrees. The ratio S1 / S2 between the area S1 of the light emitting surface 12a of the organic EL element 12 and the area S2 of the end surface 14b is 0.5 or less. With such a configuration, the light extraction efficiency of the light emitted from the EL element and incident into the transparent substrate 11 is improved as compared with the case where the shape of the light incident portion 14 is a quadrangular pyramid, and the light extraction efficiency is improved. It can be higher than the conventional device.

(9) When N is 8, that is, when the light incident portion 14 is formed in an octagonal truncated pyramid, the illumination device 10 that is relatively easy to process and has high luminance is obtained.
(Third embodiment)
Next, a third embodiment will be described. This embodiment is different from the first embodiment in that the light incident portion 14 is not a truncated cone but an elliptical truncated cone having a major axis / minor axis ratio (major axis / minor axis) of 2 or less. . The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The light incident portion 14 is formed such that the area of the end surface 14a on the organic EL element 12 side is smaller than the area of the opposite end surface 14b, and the inclination angle of the inclined surface 15 of the light incident portion 14 is 55 to 80 degrees. is there. The ratio S1 / S2 between the area S1 of the light emitting surface 12a of the organic EL element 12 and the area S2 of the end face 14b opposite to the end face 14a on the organic EL element 12 side of the light incident portion 14 is 0.5 or less.

  Table 4 shows the effect of changing the ratio of the major axis to the minor axis of the end face 14b of the light incident part 14 on the ray tracing simulation for a model having a ratio S1 / S2 of 0.09 and an inclination angle θ of 65 degrees. Shown in In Table 4, the relative luminance indicates a value when the length of the major axis and the minor axis are equal (ratio is 1), that is, when the luminance of the light incident portion 14 of the truncated cone is 1. Note that the relative luminance value is 0.65 when the light incident portion 14 is formed with a quadrangular pyramid and the sides of the adjacent end faces of the quadrangular pyramid on the organic EL element 12 side are in contact with each other. . From Table 4, it is confirmed that the luminance decreases as the ratio of the major axis to the minor axis (major axis / minor axis) increases, and when the ratio is formed on an elliptical truncated cone having a ratio of 2 or less, the luminance is higher than in the case of a quadrangular pyramid. It was done. That is, even if the light incident portion 14 is not a truncated cone but an elliptical truncated cone, if the ratio of the major axis to the minor axis is 2 or less, compared to the case where the shape of the light incident unit 14 is a quadrangular pyramid, The extraction efficiency of light emitted from the organic EL element 12 and incident on the transparent substrate 11 is improved, and the extraction efficiency of light can be increased as compared with the conventional apparatus.

実施の形態は前記に限定されるものではなく、例えば、次のように構成してもよい。

The embodiment is not limited to the above, and may be configured as follows, for example.

  The light incident part 14 does not have to be strictly a truncated cone, an elliptical truncated cone, or a polygonal truncated cone, but may be a truncated cone shape, an elliptical truncated cone shape, or a polygonal truncated cone shape. The intersection line between the plane including the central axis and the inclined surface 15 may be a curved line. The curve may be an outwardly convex curve as shown in FIG. 5 (a) or an inwardly convex curve as shown in FIG. 5 (b). When the light incident portion 14 has these shapes, the inclination angle θ of the inclined surface 15 of 55 to 80 degrees means that the curve satisfies the following requirements. That is, the straight line L1 connecting the curved edge portion CE of the organic EL element 12 and the position P1 of 40% from the edge portion of the organic EL element 12 in the thickness direction of the light incident portion 14, or the position P1 of 40%. , And at least one of the straight lines L2 connecting the 80% position P2 from the end portion on the organic EL element 12 side and the straight line L extending in a direction parallel to the end surface 14a on the organic EL element 12 side of the light incident portion 14 It means that the formed angle is 55 to 80 degrees. In these cases, as shown in FIG. 5 (a), as shown in FIG. 5 (b), the line of intersection with the inclined surface 15 of the light incident portion 14 is a convex curve outward. In addition, it is easy to improve the light extraction efficiency as compared with the case where the intersecting line is an inwardly convex curve or the intersecting line is a straight line.

  The illumination device 10 includes a transparent substrate 11 having a plurality of light incident portions 14 formed on the surface opposite to the emission surface 13 and an organic EL element provided so that the light emission sides face each other. 12, and the organic EL element 12 is not limited to the configuration in which the organic EL element 12 is directly formed on the end surface 14 a of the light incident portion 14. For example, as shown in FIG. 6, after a plurality of organic EL elements 12 are formed on the substrate 20 at positions facing the end face 14a of the light incident portion 14 of the transparent substrate 11, the organic EL element 12 side of the substrate 20 is formed. The organic EL element 12 and the light incident portion 14 may be bonded to the light incident portion 14 side of the transparent substrate 11 via an adhesive (not shown). As the adhesive, an ultraviolet curable adhesive or a polymer adhesive having the same or close refractive index as that of the transparent substrate 11 in the visible light wavelength region is used. “Near refractive index” means that the difference in refractive index is within several percent. The substrate 20 may not be transparent. In this configuration, when the adhesive has a function of a protective part, it is not necessary to provide a protective part for protecting the organic EL layer 17 from oxygen and moisture.

  The light emitting surface 12a of the organic EL element 12 is not limited to a flat surface but may be a curved surface. When the light emitting surface 12a is a curved surface, the organic EL element 12 is directly stacked on the end surface 14a of the light incident portion 14 as in the first embodiment. Then, the organic EL element 12 is formed. In the configuration in which the organic EL element 12 is formed on the substrate 20 as in another embodiment shown in FIG. 6, the portion of the substrate 20 where the organic EL element 12 is formed is formed in a curved surface.

The arrangement of the light incident portions 14 is not limited to a square lattice shape, and may be a hexagonal close-packed lattice arrangement, a regular arrangement in which the end faces 14b of the light incident portions 14 do not contact each other, or a random arrangement.
The size of the light emitting surface 12 a of the organic EL element 12 is not limited to the same size as the end surface 14 a of the light incident portion 14, and the light emitting surface 12 a may be smaller than the end surface 14 a of the light incident portion 14.

The light incident part 14 does not have to be formed in the same manner, and may have a configuration in which light incident parts 14 having different shapes are mixed.
Depending on the illuminating device, there is also a demand for the entire emission surface 13 not to have the same luminance, such that the luminance of the central portion is high or the luminance of a predetermined region is high. In such a case, the light incident portion 14 may have a configuration in which differently shaped light incident portions 14 such as a truncated cone shape, an elliptical truncated cone shape, or a polygonal truncated cone shape are actively mixed, or the ratio S1 / An illumination device having a desired luminance state can be manufactured by mixing the light incident portions 14 having different values of S2 and the inclination angle θ.

  The lighting device 10 is not limited to the backlight, but may be used for other lighting devices, or may be applied not only to the lighting device but also to a light emitting device for a display (display device). In order to obtain a light emitting device for display, a wiring pattern for selectively driving each organic EL element 12 is required. In that case, it is easier to form a wiring pattern by adopting a manufacturing method in which an organic EL element 12 formed on a substrate 20 as shown in FIG. 6 is bonded to the light incident portion 14 side of the transparent substrate 11. .

An inorganic EL element may be used instead of the organic EL element 12 as the EL element.
The organic EL element 12 is not limited to the bottom emission type, and may be formed in a top emission type. That is, in the organic EL element 12, a cathode as a first electrode, an organic EL layer, and an anode as a second electrode are sequentially formed on a substrate, and light from the organic EL layer is extracted from the second electrode. . In this case, the substrate and the first electrode may or may not be transparent to light. However, the second electrode needs to be transparent.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to any one of claims 1 to 5, the inclination angle θ is 60 to 70 degrees.

(2) In the invention described in claim 3, the N is 8.
(3) A light emitting device comprising: a transparent substrate having a plurality of light incident portions formed on a surface opposite to the light exit surface; and an electroluminescence element provided so that the light exit sides face each other. The light incident portion has a truncated cone shape, an elliptical truncated cone shape whose ratio of major axis to minor axis is 2 or less, and an N truncated pyramid shape (n is a natural number of 6 or more). Are mixed and formed such that the area of the end face on the electroluminescence element side is smaller than the area of the end face on the opposite side, the inclination angle of the slope of the light incident part is 55 to 80 degrees, A light emitting device in which a ratio S1 / S2 between an area S1 of a light emitting surface of an electroluminescent element and an area S2 of an end surface on the opposite side of the electroluminescent element side of the light incident portion is 0.49 or less.

  (4) In the invention described in the technical idea (3), the arrangement of the light incident portions having different shapes is set so that the luminance of a predetermined region is high in the light emission state of the electroluminescence element.

(A) is the partial schematic diagram of an illuminating device, (b) is the elements on larger scale of (a). The schematic diagram which shows arrangement | positioning of a light-incidence part. The diagram which shows the relationship between relative brightness | luminance and the inclination-angle of a slope. The graph which shows the influence of the reflectance of the slope with respect to a brightness | luminance. (A), (b) is a schematic diagram which shows the shape of the light-incidence part in another embodiment. The decomposition | disassembly partial schematic diagram of the illuminating device in another embodiment. The schematic diagram of a prior art. (A), (b) is a schematic diagram of another prior art, respectively.

Explanation of symbols

  θ ... tilt angle, 10 ... illuminating device, 11 ... transparent substrate, 12 ... organic EL element as EL element, 12a ... light emitting surface, 13 ... light emitting surface, 14 ... light incident portion, 14a, 14b ... end surface, 15 ... slope .

Claims (6)

A light emitting device comprising: a transparent substrate having a plurality of light incident portions formed on a surface opposite to an emission surface; and an electroluminescence element provided so that the light emission sides face each other. ,
Each of the light incident portions has a truncated cone shape or an elliptic frustum shape having a major axis / minor axis ratio of 2 or less, and is formed so as to be reduced in diameter toward the electroluminescence element side. The slope angle of the slope of the portion is 55 to 80 degrees, and the ratio S1 between the area S1 of the light emitting surface of the electroluminescent element and the area S2 of the end surface on the opposite side of the electroluminescent element side of the light incident portion / S2 is 0.5 or less.   2. The light-emitting device according to claim 1, wherein a ratio of a total area of an area S <b> 2 of the end surface on the opposite side of the electroluminescent element side of each light incident portion to the area of the emission surface of the transparent substrate is 52% or more. A light emitting device comprising: a transparent substrate having a plurality of light incident portions formed on a surface opposite to an emission surface; and an electroluminescence element provided so that the light emission sides face each other. ,
Each of the light incident portions has an N-pyramidal shape (N is a natural number of 6 or more), and is formed such that the area of the end face on the electroluminescence element side is smaller than the area of the end face on the opposite side. The inclination angle of the inclined surface of the incident portion is 55 to 80 degrees, and the ratio between the area S1 of the light emitting surface of the electroluminescent element and the area S2 of the end surface on the opposite side of the electroluminescent element side of the light incident portion. A light emitting device having S1 / S2 of 0.5 or less.   The ratio S1 / S2 between the area S1 of the light emitting surface of the electroluminescent element and the area S2 of the end surface on the opposite side of the electroluminescent element side of the light incident portion is 0.25 or less. The light emitting device according to any one of claims 1 to 3.   The said light-incidence part is formed so that the intersection line of the plane containing the center axis | shaft and the slope of the said light-incidence part may become an outward convex curve. The light emitting device according to 1.   The light emitting device according to any one of claims 1 to 5, wherein the electroluminescence element is an organic electroluminescence element.

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